We took a look at this rule and realized it was too restrictive, so we took it out. Now, you can customize your lobby experience even more for players.
Before adding some text-ture to your lobby background, keep in mind that text must not interfere with the top navigation area or include promotion of Creator Codes. Creator Rules regarding Appropriate Language (1.10) and Promotional Materials (1.15.7) apply to lobby backgrounds as well.
See the Creator Rules here:
https://www.fortnite.com/news/fortnite-island-creator-rules